In order to ensure good road characteristics and good travelling comfort (comfortable driving) for a vehicle equipped with wheels, such as an automobile, and in the special case of travelling on rough surfaces and when driving around bends, the vehicle must be provided with a well functioning system of wheel suspension, shock absorbers and springs. The springs provide elastic resistance through storing energy when they are pressed together, and this energy is damped away at least partially by means of shock absorbers which brake the relative movement between the bodywork of the vehicle and the wheel suspension and convert the spring energy to heat.
Especially between the front wheels of the vehicle, but sometimes also between its rear wheels, there is usually some type of stabilizer which prevents excessive rolling (leaning to the side) of the bodywork when driving around bends. A usual type of stabilizer is a twist or torsion spring in the shape of a torsion rod which is rotatably mounted to the car body/chassis/base plate and which extends transversely to the longitudinal axis of the car. The ends of the torsion rod are connected to the wheel suspension by lever arms and follow their suspension movements. With differently sized suspension movements of the wheels connected together through the stabilizer the stabilizer counteracts the leaning of the bodywork when driving around corners outwards in the curve and presses the inner, lighter loaded wheel against the road surface. The outer, more heavily loaded wheel at the same time gets stiffer springing which together leads to reduced lean and thereby improved road characteristics.
A wheel suspension system with active springs can regulate both the spring function and the damping function of the wheels. A plurality of different constructive solutions concerning such systems are known in the prior art. Sensors can be included in these systems which sense, for example, the vertical wheel load, the movement of the wheel and acceleration, respectively.
Signals from the sensors are normally transmnitted to an electronic control unit which controls and influences the characteristics of the constituent components in the wheel suspension system, such as springs, shock absorbers and stabilizers.
Thus it is previously known to combine shock absorbers and wheel suspension fittings to form a shock absorber/spring unit, for example, in the shape of a hydraulic shock absorber with a surrounding helical spring (spiral spring) made of steel.
It is also known from the prior art to combine a stabilizer with a separate piston and cylinder device, which is arranged to, depending on at least one vehicle parameter, regulate the influence of the stabilizer on the wheel suspension system. Such a separate piston and cylinder device requires, however, for its mounting and in order to be able to perform its working movement, a not inconsiderable space in the vehicle. Near the rear axle the fuel tank is often in the way for such a device, and in the front of the vehicle the device must be placed under the engine which often is very problematic.